Some servers are under high load, some not - just stop the attempr, and try it again. Some other server will be chosen, and the update might run faster.
Hey, why doesn't the setup (update) process do this automatically, choosing the server not stressed? 
hallo,
it might cause redundancies - someone gets 60% of 400.vps, but then, the logic will start thinking that it's too slow, and will initiate other download, starting at 0% (well, re-get might help here). anyway, it's rather problem of load-balancing on a particular server, and under normal circumstances, one http get fits perfectly.
regards,
pc